switch ISUZU TF SERIES 2004 Manual PDF

BRAKE CONTROL SYSTEM 5A-19

System Components
Electronic Hydraulic Control Unit (EHCU), four Wheel
Speed Sensors, two Warning Lamps, and G-sensor.

Electronic Hydraulic Control Unit (EHCU)

The EHCU consists of ABS control circuits, fault
detector, and a fail-safe. It drives the EHCU according
to the signal from each sensor, cancelling ABS to return
to normal braking when a malfunction has occurred in
the ABS.
The EHCU has a self-diagnosing function which can
indicate faulty circuits during diagnosis.
The EHCU is mounted on the engine compartment rear
left side. It consists of a motor, solenoid valves fail safe
relay.
Solenoid Valves: Reduces or holds the caliper fluid
pressure for each front brake or both rear brakes
according to the signal sent from the EHCU.
Buffer chamber: Temporarily holds the brake fluid that
returns from the front and rear brake so that pressure
of front brake can be reduced smoothly.
Motor: Drives the pump according to the signal from
EHCU.
Fail safe Relay: When failure occurs in ABS.
The power supply to solenoid Valve is cut.

ABS Warning Lamp


825L300001
Vehicles equipped with the Anti-lock Brake System
have an amber “ABS” warning lamp in the instrument
panel. The “ABS” warning lamp will illuminate if a
malfunction in the Anti-lock Brake System is detected
by the Electronic Hydraulic Control Unit (EHCU). In
case of an electronic malfunction, the EHCU will turn
“ON” the “ABS” warning lamp and disable the anti-lock
braking function.

The “ABS” warning lamp will turn “ON” for
approximately three seconds after the ignition switch is
to the “ON” position.
If the “ABS” warning lamp stays “ON” after the ignition
switch is the “ON” position, or comes “ON” and stays
“ON” while driving, the Anti-lock Brake System should
be inspected for a malfunction according to the
diagnosis procedure.

Wheel Speed Sensor (WSS)
It consists of a sensor and a rotor. The sensor is
attached to the knuckle on the front wheels and to the
rear wheels.
The rotor is press-fit in the axle shaft.

G-Sensor
The G-sensor detects the vehicle deceleration speed
and sends a signal to the EHCU. In 4WD operation, all
four wheels may be decelerated in almost the same
phase, since all wheels are connected mechanically.
This tendency is noticeable particularly on roads with
low friction coefficient, and the ABS control is adversely
affected.
The G-sensor judges whether the friction coefficient of
road surface is low or high, and changes the EHCU's
operating system to ensure ABS and EBD control.

Normal and Anti-lock Braking
Under normal driving conditions, the Anti-lock Brake
System functions the same as a standard power
assisted brake system. However, with the detection of
wheel lock-up, a slight bump or kick-back will be felt in
the brake pedal. This pedal “bump” will be followed by a
series of short pedal pulsations which occurs in rapid
succession. The brake pedal pulsation will continue
until there is no longer a need for the anti-lock function
or until the vehicle is stopped. A slight ticking or
popping noise may be heard during brake applications
when the anti-lock features is being used.
When the anti-lock feature is being used, the brake
pedal may rise even as the brakes are being applied.
This is also normal. Maintaining a constant force on
the pedal will provide the shortest stopping distance.

BRAKE CONTROL SYSTEM 5A-21

Computer System Service Precautions
The Anti-lock Brake System and Electronic Brake-force
Distribution interfaces directly with the Electronic
Hydraulic Control Unit (EHCU) which is a control
computer that is similar in some regards to the Engine
Control Module. These modules are designed to
withstand normal current draws associated with vehicle
operation. However, care must be taken to avoid
overloading any of the EHCU circuits. In testing for
opens or shorts, do not ground or apply voltage to any
of the circuits unless instructed to do so by the
appropriate diagnostic procedure. These circuits should
only be tested with a high impedance multimeter
5-8840-0366-0 or special tools as described in this
section. Power should never be removed or applied to
any control module with the ignition in the “ON”
position.
Before removing or connecting battery cables, fuses or
connectors, always turn the ignition switch to the “OFF”
position.

General Service Precautions
The following are general precautions which should be
observed when servicing and diagnosing the Anti-lock
Brake System and/or other vehicle systems. Failure to
observe these precautions may result in Anti-lock Brake
System and Electronic Brake-force Distribution
damage.
 If welding work is to be performed on the vehicle
using an electric arc welder, the EHCU and valve
block connectors should be disconnected before
the welding operation begins.
 The EHCU and valve block connectors should
never be connected or disconnected with the
ignition “ON”.
Note:
 If only rear wheels are rotated using jacks or drum
tester, the system will diagnose a speed sensor
malfunction and the “ABS and Brake” warning lamp
will illuminate. But actually no trouble exists. When
the DTC is not detected and the ABS and BRAKE
warning lamp is on, “How to erase code” is
performed and a ABS and BRAKE warning lamp
are off.
If the battery has been discharged
The engine may stall if the battery has been completely
discharged and the engine is started via jumper cables.
This is because the Anti-lock Brake System (ABS) and
Electronic Brake-force Distribution (EBD) System
requires a large quantity of electricity. In this case, wait
until the battery is recharged, or set the ABS and EBD
to a non-operative state by removing the fuse for the
ABS. After the battery has been recharged, stop the
engine and install the ABS fuse. Start the engine again,
and confirm that the ABS warning Lamp does not light.
Note on Intermittents
As with virtually any electronic system, it is difficult to
identify an intermittent failure. In such a case
duplicating the system malfunction during a test drive or
a good description of vehicle behavior from the
customer may be helpful in locating a “most likely”
failed component or circuit. The symptom diagnosis
chart may also be useful in isolating the failure. Most
intermittent problems are caused by faulty electrical
connections or wiring. When an intermittent failure is
encountered, check suspect circuits for:
 Suspected harness damage.
 Poor mating of connector halves or terminals not
fully seated in the connector body (backed out).
 Improperly formed or damaged terminals.

Test Driving ABS Complaint Vehicles
In case that there has been an abnormality in the
lighting pattern of “ABS” warning lamp, the fault can be
located in accordance with the “DIAGNOSIS BY “ABS”
WARNING LAMP ILLUMINATION PATTERN”. In case
of such trouble as can be detected by the driver as a
vehicle symptom, however, it is necessary to give a test
drive following the test procedure mentioned below,
thereby reproducing the symptom for trouble diagnosis
on a symptom basis:
1.
Start the engine and make sure that the “ABS” W/L
goes OFF. If the W/L remains ON, it means that
the Diagnostic Trouble Code (DTC) is stored.
Therefore, read the code and locate the fault.
Note: The DTC cannot be cleared if the vehicle speed
does not exceed about 6km/h (4mph) at DTC, even
though the repair operation is completed.
2. Start the vehicle and accelerate to about 30 km/h
(19 mph) or more.
3. Slowly brake and stop the vehicle completely.
4. Then restart the vehicle and accelerate to about 40
km/h (25 mph) or more.
5. Brake at a time so as to actuate the ABS and stop
the vehicle.
6. Be cautious of abnormality during the test. If the
W/L is actuated while driving, read the DTC and
locate the fault.
7. If the abnormality is not reproduced by the test,
make best efforts to reproduce the situation
reported by the customer.
8. If the abnormality has been detected, repair in
accordance with the “SYMPTOM DIAGNOSIS” .
Note:

Be sure to give a test drive on a wide, even road
with a small traffic.
 If an abnormality is detected, be sure to suspend
the test and start trouble diagnosis at once.

5A-22 BRAKE CONTROL SYSTEM

“ABS” Warning Lamp
When ABS and trouble occurs to actuate “ABS”
warning lamp, the trouble code corresponding to the
trouble is stored in the EHCU. Only ordinary brake is
available with ABS being unactuated. Even when
“ABS” warning lamp is actuated, if the starter switch is
set ON after setting it OFF once, the EHCU checks up
on the entire system and, if there is no abnormality,
judges ABS to work currently and the warning lamp is lit
normally even though the trouble code is stored.
NOTE: Illumination of the “ABS” warning lamp indicates
that anti-lock braking is no longer available. Power
assisted braking without anti-lock control is still
available.

Normal Operation
“ABS ” Warning Lamp
When the ignition is first moved from “OFF” to “RUN”,
the amber “ABS” warning lamp will turn “ON”. The
“ABS” warning lamp will turn “ON” during engine
starting and will usually stay “ON” for approximately
three seconds after the ignition switch is returned to the
“ON” position. The warning lamp should remain “OFF”
at all other times.

Brake (EBD) Warning Lamp

825L300001
Vehicles equipped with the EBD (Electronic Brake-force
Distribution) System have an have “Brake” warning
lamp in the instrument panel.
If ABS warning lamp and Brake warning lamp are turn
"ON", then EBD is failed. ( Parking brake switch is
"OFF")
In the following conditions, EBD warning lamp is "ON".
 Starter switch is "ON", engine "OFF".
( Parking brake switch is "OFF")
If engine is started, then EBD warning lamp is "OFF".
( Parking brake switch is "OFF")

5A-26 BRAKE CONTROL SYSTEM

DATA LIST (Tech 2)
The data displayed by DATA LIST are as follows:


Strings Units Description 2WD 4WD
Front Left Wheel Speed km/h (MPH)
Front Right Wheel Speed km/h (MPH)
Rear Left Wheel Speed km/h (MPH)
Rear Right Wheel Speed km/h (MPH) Start the vehicle and make sure of linear
change in each wheel speed
Brake Switch Open/Closed Brake switch is “closed” when brake pedal is
stepped on.
ABS Warning Lamp On/Off To be “Off” usually
EBD Warning Lamp On/Off To be “Off” usually
ABS Stop State On/Off To be “Off” usually
ABS Relay Active/Inactive To be “Active” usually
Return Pump Active/Inactive To be “Inactive” usually
DTC Status No DTC To be “No DTC” usually
4 Wheel Drive Status Yes/No To be “Yes” usually
-
FL Dump Valve Commanded
(Front Left) Active/Inactive
FL Isolation Valve Commanded
(Front Left) Active/Inactive
FR Dump Valve Commanded
(Front Right) Active/Inactive
FR Isolation Valve Commanded
(Front Right) Active/Inactive
Rear Dump Valve Commanded Active/Inactive
Rear Isolation Valve Commanded Active/Inactive
FL Dump Valve Feedback
(Front Left) Active/Inactive
FL Isolation Valve Feedback
(Front Left) Active/Inactive
FR Dump Valve Feedback
(Front Right) Active/Inactive
FR Isolation Valve Feedback
(Front Right) Active/Inactive
Rear Dump Valve Feedback Active/Inactive
Rear Isolation Valve Feedback Active/InactiveEach valve is “Active” when each valve is
opereted.
G-Sensor Output V 2.0~3.0V when vehicle speed is 0 km/h (flat
place) -
Battery Voltage V The voltage value currently supplied to EHCU
Diagnostics Connector Open/Closed Diagnostics connector is “Open” when
diagnostics connector is connected.

BRAKE CONTROL SYSTEM 5A-33

How to display and erase DTCs:
Note:
 DTCs can be displayed also by TECH 2 use
“Diagnostic Trouble Codes“ mode.
1. How to start DTC display:
 Confirm that the vehicle has come to a
complete stop (with the wheels standing still)
and that the brake pedal is not depressed.
(Unless these two condition are satisfied, DTC
display cannot be started.)
 With IGN OFF, connect #12 terminal with #4
terminal or # 5 terminal (GND) . Then turn IGN
ON.

The DLC is located behind the driver side kick panel

















This illustration is based on RHD model
350L300005

 Keep #12 terminal connected with #4 terminal
or # 5 terminal (GND) during DTC display. (If
#12 terminal is separated from #4 terminal or #
5 terminal (GND) during display, display will
stop.)
2. DTC display:
 DTC is displayed by blinking warning lamp.
 Double-digit display.
 First, normal DTC 12 is displayed three times
and then any other DTCs are displayed three
times. (If no other DTCs have been stored, the
display of DTC 12 will be repeated.)
3. How to erase code:
 Conduct brake switch ON/OFF operation 6 or
more times within 3 seconds of self-diagnosis
startup.
 The code cannot be erased if more than 3
seconds have passed since self-diagnosis
startup, or if self-diagnosis has started with
brake switched on (brake pedaled).
B05RW0005

5A-34 BRAKE CONTROL SYSTEM

4. Notes
 If the following should occur during Diagnostic
Trouble Code (DTC) display, the display will be
discontinued. After initial check, the status that
is under the control of ABS will be returned :
– The vehicle starts (The wheels turn) or the
brake pedal is depressed.
 Up to 3 different codes can be stored.
 If the ABS should turn OFF due to an
intermittent defect, the system will be restored
at the next key cycle, if the initial check finds no
abnormality (when IGN is switched from OFF to
ON).
5. An example of DTC display
Display of DTC 23

B05R100001
After displaying DTC 12 three times, one DTC after
another is displayed. DTC is displayed on small
order.

C05L300017
The DTC 12 is displayed repeatedly.

BRAKE CONTROL SYSTEM 5A-35

Basic Diagnostic Flow Chart

RTW45AMF000101

Step Action Value(s) Yes No
1 1. Ignition “ON,”engine “OFF.”
2. Observe the ABS warning lamp.
Note: If a starter switch is turned ON, ABS warning
lamp will turn on and a ABS warning lamp will be
turned off after 3 seconds.
Is the ABS warning lamp “ON”?
- Go to Step 2 Go to “No
ABS warning
lamp”
2 1. Ignition “OFF.”
2. Install Tech2.
3. Ignition “ON.”
4. Attempt to display ABS data with the Tech 2.
Does the Tech 2 display ABS data?
- Go to Step 5 Go to Step 3
3 1. Ignition “OFF,” disconnect the EHCU.
2. Check the DLC (Data Link Connector) circuit for an
open, short to ground, or short to voltage.
Also, check the DLC ignition feed circuit for an
open or short to ground and the DLC ground circuit
for an open.
3. If a problem is found, repair as necessary.
Was a problem found?
- Go to Step 2 Go to Step 4

BRAKE CONTROL SYSTEM 5A-41

Brake Pedal Feed Is Abnormal

Step Action
Value(s) Yes No
1 Is the stop light actuated when the brake pedal is
depressed?
- Go to Step 2 Go to Step 3
2 1. Turn the ignition switch off.
2. Disconnected EHCU connector.
Is the check voltage for EHCU connector terminals
when brake pedal is depressed than battery voltage?
- Go to Step 4 Harness NG
between stop
light SW and
EHCU.
Go to Step 6
3 Is stop light fuse normal?
- Go to Step 5 Replace stop
light fuse.
Go to Step 6
4 Is the check continuity between EHCU connector to
body grounded?
- Go to Step 6 Repair body
grounded
harness.
Go to Step 6
5 Is stop light switch operation normal?
- Repair stop
light harness.
Go to Step 6 Replace stop
light switch.
Go to Step 6
6 Reconnect all components, ensure all components
are properly mounted.
Was this step finished?
- Repeat the
“Basic
diagnostic
flow chart” Go to Step 6

5A-42 BRAKE CONTROL SYSTEM

Braking Sound (From EHCU) Is Heard While Not Braking

Step Action Value(s) Yes No
1 Is this the first vehicle start after engine start?
- It is self
checking
sound
Normal. Go to Step 2
2 Is vehicle speed under 10 km/h?
- It is self
checking
sound
Normal. Go to Step 3
3 Check for the following condition:
 At the time of shift down or clutch operation.
 At the time of low road friction drive (ice or snow
road) or rough road drive.
 At the time of high-speed turn.
 At the time of passing curb.
 At the time of operating electrical equipment
switches.
 At the time of racing the engine.
Did it occur under any one condition above?
- ABS may
sometimes be
actuated even
when brake
pedal is not
applied. Go to Step 4
4 Is there play in each or any sensor/wheel speed
sensor rotor?
- Repair.
Go to Step 7 Go to Step 5
5 Damage or powdered iron sticking to each or any
sensor/wheel speed sensor rotor?
- Repair.
Go to Step 7 Go to Step 6
6 Is each sensor normal?
Note : Check the EHCU type for specification, the
EHCU is replaced.
(Specification; 2WD or 4WD Model)

- Check
harness/
connector for
suspected
disconnection
If no
disconnection
is found,
replace EHCU
Go to Step 7 Repair.
Go to Step 7
7 Reconnect all components, ensure all components
are properly mounted.
Was this step finished?
- Repeat the
“Basic
diagnostic
flow chart” Go to Step 7

BRAKES 5C-31

ADJUSTMENT PROCEDURE OF BRAKE PEDAL



The push rod serves as the brake pedal stopper when the
pedal is fully released.
Brake pedal height adjustment should be performed as follows.

RTW35CSH000601


Brake Pedal - Height
Measure the brake pedal height after making sure the pedal is
fully returned by the pedal return spring.
Note:
Pedal height (L2) must be measured after starting the
engine and increasing the revolution several times by
stepping on the accelerator pedal.
mm(in)

Pedal free play (L1) 6-10 (0.23 - 0.39)
M/T 174-186 (6.85-7.32)
RHD
LHD
A/T 176-188 (6.93-7.40) Height (L2)
Note:
Pedal free play must be measured after turning off the
engine and stepping on the brake pedal firmly five times
or more.
If the measured value deviates from the above range, adjust
the brake pedal as follows:
a) Disconnect the stop lamp switch.
b) Loosen the lock nut on the push rod.
c)
Adjust the brake pedal to the specified height by rotating the
push rod in the appropriate direction.



Lock Nut Torque N

m(kgf

m/lb
 
ft)
12 - 18 (1.2 – 1.8 / 9 - 13)

d) Install the stop lamp switch.

Note:
Pedal height (L
2) must be 80 mm (3.14 in.) or more when
applying about 50 kg (110.25 lbs.) of stepping force.

331R300005


How to connect the CLEVICE of BOOSTER ROD with PEDAL
ARM. and how to adjust the PEDAL SW.
After connecting the CLEVIS of BOOSTER ROD with PEDAL
ARM, adjust the PEDAL SW mounted (PDA) to PEDAL
BRACKET by the procedure explained still more bellow.
1. Set the hole of the CLEVIS of BOOSTER&M/CYL ROD
with the hole of the PEDAL ARM.
2. Enter the PIN; PUSH ROD to PEDAL to these holes
from left side of the PEDAL.
3. Enter and fix the PIN; SANP PIN FIX to the DITCH o
f
the PIN; PUSH ROD to PEDAL from right side of the
PEDAL.
4. Release the LOCK by turning the SWITCH counter-
clock-wise.